swift - 对相机胶卷上图像文件的文件访问(iOS 12.1.4、Swift 4.2、Xcode 10.1)

Question

我试图在使用内置相机拍照后计算 JPEG 文件(例如 MD5)的文件哈希值。我可以对图像数据创建摘要，但这与实际文件哈希不同。查看 Photo 模块及其 PHAsset 类，我没有找到一种方法来检索实际文件路径 (URL)，然后将其提供给 MD5Digest。也许可以通过实现完成监听器功能，在将图像保存到相机胶卷后立即捕获文件URL。有人尝试过吗？

使用completionHandler更新了代码，但我仍然需要找到URL。

 @IBOutlet weak var imageHash: UILabel!

func imagePickerController(_ picker: UIImagePickerController, didFinishPickingMediaWithInfo info: [UIImagePickerController.InfoKey : Any]) {

    let orgPic = info[UIImagePickerController.InfoKey.originalImage] as? UIImage

    UIImageWriteToSavedPhotosAlbum(orgPic!, self, #selector(imageSaved(_:didFinishSavingWithError:contextInfo:)), nil)

}

@objc func imageSaved(_ img: UIImage, didFinishSavingWithError error: NSError?, contextInfo: UnsafeRawPointer) {
        if let error = error {
            // we got back an error!
            let ac = UIAlertController(title: "Save error", message: error.localizedDescription, preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        } else {
            let ac = UIAlertController(title: "Saved!", message: "\(img.ciImage?.url)", preferredStyle: .alert)
            ac.addAction(UIAlertAction(title: "OK", style: .default))
            present(ac, animated: true)
        }
 }

// the img.ciImage.url is "nil" unfortunately

Answer 1

所以你的主要座右铭是比较 2 个图像文件的 MD5。这就是我尝试过的方法，也许会对您有所帮助

;TLDR - 库中保存的文件和实际文件与我不匹配

 public func saveImgToLocal(_ img: UIImage,
                           onComplete: @escaping () -> Void) {

    var blockPlaceholder: PHObjectPlaceholder?
    var changeRequest: PHAssetChangeRequest?

    PHPhotoLibrary.shared().performChanges({
        changeRequest =  PHAssetChangeRequest.creationRequestForAsset(from: img)
        blockPlaceholder = changeRequest?.placeholderForCreatedAsset
    }, completionHandler: { (saved, error) in
        //_saved_ is of type bool, you can use it to check whether image is saved
        //Here we would fetch the asset using our saved placeholder
        let fetchOptions = PHFetchOptions()
        let fetchResult:PHFetchResult = PHAsset.fetchAssets(withLocalIdentifiers: [blockPlaceholder!.localIdentifier], options: fetchOptions)
        if let asset = fetchResult.firstObject {
            //Method to convert asset to Actual image
            self.getAsset(asset: asset)
        }
        onComplete()

    })
}

这就是我将图像保存到本地的方法

这就是我从本地获取图像的方式

func getAsset(asset: PHAsset)  {
    let manager = PHImageManager.default()
    let option = PHImageRequestOptions()
    var resultImage = UIImage()
    option.isSynchronous = true
    manager.requestImage(for: asset, targetSize: PHImageManagerMaximumSize, contentMode: .aspectFit, options: option, resultHandler: {(result, info)->Void in
        resultImage = result!
        let url = info!["PHImageFileURLKey"] as! NSURL
        //Image created using the file URL.
        let image = UIImage.init(contentsOfFile: url.path!)
//I even compared the resultImage instead of the image from the file
        if UIImagePNGRepresentation(image!) == UIImagePNGRepresentation(self.image!) {
            print("Same image")
        }
    })

}

因此，如果您只想取回保存的图像，这是可以做到的，但我不确定图像是否按原样保存在照片库中。呵呵:-)